Stephens beat Parmentier 7-6 (7-3) 7-5 but it was a tough opener for the holders in front of a raucous home crowd that included former world No 1 Amelie Mauresmo.

Parmentier raced out to a 5-2 lead in the opener but failed to take five set-point opportunities, allowing her opponent to rally before taking the lead courtesy of a tie-break.

Stephens was pushed hard in the second set too, fighting back from a break down to clinch victory with a crunching forehand winner in the 12th game.

However, team-mate Coco Vandeweghe blew a one-set lead against Mladenovic, who snapped her opponent's 13-rubber winning streak in the competition with an impressive 1-6 6-3 6-2 triumph.

HALEP SURVIVES SCARE

The pressure was on world number one Simona Halep as she opened up for Romania, and she survived a scare to ease past Switzerland's Viktorija Golubic 6-3 1-6 6-1.

Halep was broken in the first game of the match and lost five in a row in the second set, but she dug deep to give Romania a 1-0 advantage, with Irina-Camelia Begu putting them in the driving seat for a World Group place next year with victory over Timea Bacsinszky.

In the World Group II play-offs, French Open champion Jelena Ostapenko beat Ekaterina Makarova as Latvia finished day one against Russia 1-1, while Spain – led by Garbine Muguruza – hold a 2-0 lead over Paraguay.